Compositions and methods for reducing fire hazard of flammable refrigerants

ABSTRACT

The present invention relates to compositions comprising flammable refrigerant, fire hazard-reducing agent, and optionally a lubricant suitable for use in a refrigeration or air conditioning apparatus. Further, the present invention relates to compositions comprising lubricant and fire hazard-reducing agent and methods for reducing flammability of flammable refrigerant, for delivering a fire hazard-reducing agent to a refrigeration or air conditioning apparatus, and for replacing a non-flammable refrigerant with a flammable refrigerant.

CROSS REFERENCE(S) TO RELATED APPLICATION(S)

This application is a divisional application of and claims the prioritybenefit of U.S. patent application Ser. No. 12/488,701, filed Jun. 22,2009, now granted as U.S. Pat. No. 7,867,410, which is a divisional ofand claims priority benefit of U.S. patent application Ser. No.10/987,250, granted on Nov. 12, 2004 as U.S. Pat. No. 7,560,044, whichclaims priority benefit of U.S. Provisional Patent Application No.60/519,689, filed Nov. 13, 2003.

FIELD OF THE INVENTION

The present invention relates to refrigerant compositions comprisingfire hazard-reducing agents. The compositions of the present inventionare suitable replacements for non-flammable, refrigerant compositions,including the refrigerants used in automobile air conditioning systems.

BACKGROUND OF THE INVENTION

Hydrofluorocarbon (HFC) refrigerants have become widely used inrefrigeration and air-conditioning apparatus throughout the world. HFCsbecame the refrigerant of choice as first chlorofluorocarbons and nowhydrochlorofluorocarbons have been phased out due to their deleteriouseffect on the ozone layer. HFC refrigerants were developed asintermediate replacements, but some have been identified as having highglobal warming potential (GWP). New regulations relating to GWP arebeing adopted thereby requiring the industry to move to alternativerefrigerants having an acceptable GWP.

Several types of molecules have been in use or proposed for use in placeof the high GWP refrigerants. Many low GWP alternative refrigerants haveissues related to toxicity or flammability. The industry has avoided theuse of flammable refrigerants in many regions in the world due to thesafety factor particularly with respect to consumer products used inhomes and automobiles.

It is the object of the present invention to identify means by whichflammable refrigerants could be used as replacements for the higherglobal warming refrigerants currently in use. If currently availableflammable refrigerants are used in place of existing refrigerants, thecost of this conversion can be minimized and the ultimate savings willbe to the consumer.

Many of the refrigerant blends being sold to replace CFCs or HCFCs havebeen formulated such that they are non-flammable. But it is often thenon-flammable component of the blend that contributes most to theblend's GWP. The higher number of fluorine atoms on the molecule reducesthe flammability, but also increases the GWP. The more flammable HFCshave a lower number of fluorines (and thus lower GWP), but thecorresponding increase in the number of hydrogens yields a flammablecompound.

The art discloses many compositions as having particular utility in therefrigeration and air-conditioning industry due to their non-flammablenature. Many of these compositions are made non-flammable by way ofdilution of the flammable component with a known non-flammablerefrigerant.

The present invention addresses flammability of the entire refrigerantcomposition. Often times, the lubricant, which is necessary in mostvapor compression refrigeration or air-conditioning systems, iscombustible. The present invention addresses this issue by providingcompositions that have reduced overall flammability when consideringboth the refrigerant and the refrigerant/lubricant compositions ascompared to those compositions available at present.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to a composition comprising: at least oneflammable refrigerant; at least one fire hazard-reducing agent. Thecomposition may also comprise a lubricant suitable for use withrefrigeration or air-conditioning apparatus.

The present invention further relates to a composition comprising: afire hazard-reducing agent and a lubricant suitable for use withrefrigeration or air conditioning apparatus.

A further disclosure of the present invention is a method for deliveringa fire hazard-reducing agent into a refrigeration or air conditioningapparatus, said method comprising: combining said agent with arefrigerant suitable for use in refrigeration or air conditioningapparatus; or combining said agent with a lubricant suitable for use inrefrigeration or air conditioning apparatus; or introducing said agentinto said refrigeration or air conditioning apparatus.

Also disclosed herein is a method for reducing fire hazard in or in thevicinity of a refrigeration or air conditioning apparatus, said methodcomprising: combining a fire-reducing agent with a flammablerefrigerant; or combining fire-reducing agent with a lubricant; andintroducing either combination into a refrigeration or air conditioningapparatus.

Also disclosed herein is a method of using a fire hazard-reducing agentin refrigeration or air conditioning apparatus, said method comprising:combining said agent with a flammable refrigerant suitable for use inrefrigeration or air conditioning apparatus; or combining said agentwith a lubricant suitable for use in refrigeration or air conditioningapparatus; or introducing said agent into refrigeration or airconditioning apparatus.

Another embodiment of the present invention is a composition, saidcomposition being suitable for replacing non-flammable refrigerant inrefrigeration or air conditioning apparatus, comprising: flammablerefrigerant; fire-hazard reducing agent; and optionally a lubricant.

Yet another embodiment of the present invention is a method forreplacing a non-flammable refrigerant with a flammable refrigerant in arefrigeration or air conditioning apparatus, said method comprisingadding a fire hazard-reducing agent to said flammable refrigerant.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to compositions and methods that areuseful to reduce fire-hazard in refrigerant compositions, inrefrigeration and/or air conditioning systems, or in the vicinity ofsuch systems. Flammable refrigerants of the present invention compriseany compound which may be demonstrated to propagate a flame underspecified conditions of temperature, pressure and composition when mixedwith air. Flammable refrigerants may be identified by testing underconditions specified by ASHRAE (American Society of Heating,Refrigerating and Air-Conditioning Engineers, Inc.) Standard 34-2001,under ASTM (American Society of Testing and Materials) E681-85, exceptthat the ignition source shall be an electrically activated kitchenmatch head. Such tests of flammability are conducted with therefrigerant at 101 kPa (14.7 psia) and 21° C. (70° F.) at variousconcentrations in air in order to determine the lower flammability limit(LFL) and upper flammability limit (UFL) of the test compound in air.

In practical terms, a refrigerant may be classified as flammable if uponleaking from a refrigeration or air conditioning apparatus, andcontacting an ignition source a fire may result. The compositions of thepresent invention, during such a leak, have a lower probability ofcausing a fire.

Flammable refrigerants of the present invention includehydrofluorocarbons (HFCs), fluoroethers, hydrocarbon ethers,hydrocarbons, ammonia and mixtures thereof. Representative HFCrefrigerants include but are not limited to: difluoromethane (HFC-32),fluoromethane (HFC-41), 1,1,1-trifluoroethane (HFC-143a),1,1,2-trifluoroethane (HFC-143), 1,1-difluoroethane (HFC-152a),fluoroethane (HFC-161), 1,1,1-trifluoropropane (HFC-263fb), and mixturesthereof. HFC refrigerants are commercial products available from anumber of sources such as E.I. du Pont de Nemours & Co. (DuPont)Wilmington, Del., 19898, USA, or are available from custom chemicalsynthesis companies such as PCR Inc., P.O. Box 1466, Gainesville, Fla.,32602, USA, and additionally by synthetic processes disclosed in artsuch as The Journal of Fluorine Chemistry, or Chemistry of OrganicFluorine Compounds, edited by Milos Hudlicky, published by The MacMillanCompany, New York, N.Y., 1962.

Flammable refrigerants of the present invention further comprisefluoroethers, compounds similar to hydrofluorocarbons, which alsocontain at least one ether group oxygen atom. A representativefluoroether refrigerants includes but is not limited to C₄F₉OC₂H₅(3M™,St. Paul, Minn.).

Flammable refrigerants of the present invention further comprisehydrocarbon refrigerants. Representative hydrocarbon refrigerantsinclude but are not limited to propane, propylene, cyclopropane,n-butane, isobutane, and n-pentane. Hydrocarbon refrigerants are readilyavailable from multiple commercial sources.

Flammable refrigerants of the present invention further comprisehydrocarbon ethers, such as dimethyl ether (DME) sold by DuPont,Wilmington, Del.

Flammable refrigerants of the present invention further comprise ammonia(NH₃), which is readily available from multiple commercial sources.

Flammable refrigerants of the present invention may further comprisemixtures of more than one refrigerant such as a mixture of two flammablerefrigerants (eg. two HFCs or an HFC and a hydrocarbon) or a mixturecomprising a flammable refrigerant and a non-flammable refrigerant, suchthat the overall mixture is still considered to be a flammablerefrigerant.

Examples of non-flammable refrigerants that may be combined with otherrefrigerants of the present invention include R-134a, R-23, R125,R-236fa, R-245fa, and mixtures of HCFC-22/HFC-152a/HCFC-124 (known bythe ASHRAE designations, R-401A, R-401 B, and R-401C),HFC-125/HFC-143a/HFC-134a (known by the ASHRAE designation, R-404A),HFC-32/HFC-125/HFC-134a (known by ASHRAE designations, R-407A, R-407B,and R-407C), HCFC-22/HFC-143a/HFC-125 (known by the ASHRAE designation,R-408A), HCFC-22/HCFC-124/HCFC-142b (known by the ASHRAE designation:R-409A), HFC-32/HFC-125 (R-410A), and HFC-125/HFC-143a (known by theASHRAE designation: R-507) and carbon dioxide.

Examples of mixtures of more than one flammable refrigerant includepropane/isobutane; HFC-152a/isobutane, R32/propane; R32/isobutane;HFC-32/ammonia, HFC-125/ammmonia and HFC-32/HFC-125/ammonia andHFC/carbon dioxide mixtures such as HFC-152a/CO₂.

By fire hazard-reducing agent is meant any additive which upon additionto a flammable refrigerant or flammable refrigerant/lubricantcomposition reduces the flammability of the composition as determinedand defined by the methods and standards described previously herein. Ina practical sense, refrigerant that may leak from an air conditioning orrefrigeration system is one major concern when considering flammability.Should a leak occur in a refrigeration system, refrigerant andpotentially a small amount of lubricant may be released from the system.If this leaking material may come in contact with an ignition source, afire may result. The fire hazard-reducing agents of the presentinvention reduce the probability of a fire in the event of a leak and/orreduce the degree of fire hazard by reducing the temperature or size ofany flame produced.

Fire hazard-reducing agents of the present invention comprise salts(e.g. acetates, borates, carbonates, bicarbonates, phosphates, nitrates,hydroxides, oxides, molybdates, bromides, bromates, chlorates,chlorides, or iodides), phosphorous compounds including phosphateesters, organic phosphonates, and phosphonium salts, boric acid, organicboron compounds, brominated compounds, chlorinated paraffins, ammoniumpolyphosphates, melamines, mixtures of water with polyalkylene glycolsor polyol esters, perfluorinated lubricants, fluoroketones, fluoroiodocompounds, or mixtures thereof.

Representative fire-hazard reducing salt agents of this type include butare not limited to: sodium acetate (CH₃CO₂Na), potassium acetate(CH₃CO₂K), potassium carbonate (K₂CO₃), iron (II) carbonate (FeCO₃),sodium carbonate (Na₂CO₃), ammonium carbonate ((NH₄)₂CO₃), sodiumbicarbonate (NaHCO₃), potassium bicarbonate, (KHCO₃), ammonium phosphate((NH₄)₃PO₄), potassium nitrate (KNO₃), sodium chloride (NaCl), potassiumchloride (KCl), cobalt chloride (CoCl₂), rubidium chloride (RbCl),titanium chloride (TiCl₄), sodium bromide (NaBr), potassium bromide(KBr), rubidium bromide (RbBr), potassium iodide (KI), rubidium iodide(RbI), magnesium hydroxide (Mg(OH)₂), aluminum hydroxide (Al(OH)₃), zincborate (3ZnO:2B₂O₃), zinc oxide (ZnO), zinc molybdate (ZnMoO₄), calciummolybdate (CaMoO₄), copper oxides, (Cu₂O and CuO), and antimony oxides,including but not limited to antimony trioxide (Sb₂O₃) and antimonypentoxide (Sb₂O₅), and others. Such salts are available from manychemical suppliers such as Aldrich, Milwaukee, Wis.

Fire hazard-reducing agents of the present invention further comprisephosphorus compounds. Such phosphorus compounds include phosphateesters, including but not limited to: trialkyl phosphates, triarylphosphates, mixed alkyl-aryl phosphates (alkyldiaryl, dialkylaryl oralkylated aryl), and cyclic phosphates. Representative trialkylphosphates include: trimethyl phosphate ((CH₃)₃PO₄, Cas reg. no.512-56-1); triethyl phosphate ((CH₃CH₂)₃PO₄, Cas reg. no. 78-40-0);tributyl phosphate ((C₄H₉)₃PO₄, CAS reg. no. 126-73-8); trioctylphosphate((C₈H₁₇)₃PO₄, CAS reg. no. 1806-54-8); andtri(2-ethylhexyl)phosphate ((CH₃CH(C₂H₅)(CH₂)₄)₃PO₄, CAS reg. no.78-42-2). Representative triaryl phosphates include: triphenyl phosphate((C₆H₅O)₃PO, CAS reg. no. 115-86-6); tricresyl phosphate (TCP,(CH₃C₆H₄O)₃PO, CAS reg. no. 1330-78-5); and trixylenyl phosphate(((CH₃)₂C₆H₃O)₃PO, CAS reg. no. 25155-23-1). Representative mixedalkyl-aryl phosphates include: isopropylphenyl phenyl phosphate (IPPP,(C₆H₅O)₂((CH₃)₂CHO)PO, CAS reg. no. 68782-95-6) and bis(t-butylphenyl)phenyl phosphate (TBPP, (C₆H₅O)₂((CH₃)₃C)PO, CAS reg. no. 65652-41-7).Such phosphorus compounds are available from multiple chemical supplierssuch as Aldrich (Milwaukee, Wis.); Alfa Aesar (Ward Hill, Mass.); orAkzo Nobel (Arnhem, the Netherlands). Additional representativephosphorus compounds are Syn-O-Ad 8784, a butylated triphenyl phosphatefrom Akzo Nobel (Arnhem, the Netherlands); Durad 620, a tert-butylatedtriphenyl phosphate from Great Lakes Chemical Corporation (GLCC, WestLafayette, Ind.); and Durad 220 and 110, iso-propylated triphenylphosphates also from GLCC.

Fire hazard-reducing agents of the present invention further compriseorganic phosphonates and phosphonium salts. Representative organicphosphonates and phosphonium salts include: tris monochloropropylphosphate (TMCPP, different isomers, tris(2-chloroisopropyl) phosphate,Cas reg. no. 13674-84-5, and tris(2-chloropropyl) phosphate, Cas reg.no. 6145-73-9); tris (1,3-dichloro-2-propyl) phosphate (TDCPP,P(OCH₂OH)₄Cl, CAS reg. no. 13674-87-8); dimethyl phosphonate(PHO(OCH₃)₂, Cas reg no. 868-85-9); andtetrakis(hydroxymethyl)phosphonium chloride (P(CH₂OH)₄Cl, CAS reg. No.124-64-1) among others. These phosphorus compounds are also availablefrom Aldrich, Alfa Aesar, or Akzo Nobel.

Fire hazard-reducing agents of the present invention further compriseother boron compounds such as boric acid (H₃BO₃, Cas reg. no.10043-35-3), triphenyl borane (B(C₆H₅)₃, Cas reg. no. 960-71-4) andother boron salts, such as sodium borate.

Fire hazard-reducing agents of the present invention further comprisebrominated organic compounds such as hexabromocyclododecane (Cas reg.no. 25637-99-4) or decabromodiphenyl oxide (Cas reg. no. 1163-19-5). Thebrominated organic compounds of the present invention further includealiphatic compounds such as dibromoneopentyl glycol (DBNPG,C(CH₂BR)₂(CH₂OH)₂, Specialchem FR-522, Cas reg. no. 3296-90-0);trisbromoneopentyl phosphate (Specialchem FR-370/FR-372,(C(CH₂Br)₃CH₂O)PO, Cas reg. no. 19186-97-1), trisbromoneopentyl alcohol(TBNPA, CH₂(CH₂Br)OH, Cas reg. no. 36483-57-5), andhexabromocyclododecane (HBCD,cyclo-(—CHBrCHBrCH₂CH₂CHBrCHBrCH₂CH₂CHBrCHBrCH₂CH₂—), Cas reg. no.25637-99-4).

The brominated organic compounds of the present invention furtherinclude aromatic compounds such as decabromodiphenyl oxide (DECA,O(C₆Br₅)₂, Specialchem FR-1210, Cas reg. no. 1163-19-5);tris(tribromophenyl)triazine (Cas reg. no. 25713-60-4, SpecialchemFR-245); tetrabromobisphenol A bis (2,3-dibromopropyl ether)(Specialchem FR-720, Cas reg. no. 21850-44-2); Octabromodiphenyl oxide(OCTA, Cas reg. no. 32536-52-0, Specialchem FR-1208);tetrabromobisphenol A (CH₃)₂C(C₆H₂Br₂OH)₂, Cas reg. no. 79-94-7,Specialchem FR-1524); and brominated trimethylphenyl indan (Cas reg. no.155613-93-7, Specialchem FR-1808).

The brominated organic compounds of the present invention furtherinclude brominated epoxy compounds such as Specialchem F-2016 (oligomer,Cas reg. no. 68928-70-1), among others. All of the aliphatic brominated,aromatic brominated and brominated epoxy compounds listed above areavailable from Specialchem S.A. (Paris, France).

Fire hazard-reducing agents of the present invention further comprisechlorinated paraffins with 10-30 carbon atoms and having from about 35weight percent to about 70 weight percent chlorine in the molecule.Chlorinated paraffins of the present invention include TheChlorez®/Hordaresin® flame retardant additives, Doversperse® dispersionsand emulsions of resinous and liquid chlorinated paraffins, Doverguard®brominated chlorinated paraffins, Paroil®, and Chlorowax® liquidchlorinated paraffins, all produced by Dover Chemical Corporation(Dover, Ohio). Additionally, chlorinated paraffins of the presentinvention include Cereclor® 42, 42SS, 48, 70, LCCP 44, and 46 fireretardant chlorinated paraffin waxes and Cereclor® S-45, 51 L, S-52,S-52HV, S-55, S-56, S-56B, and MCCP 54 C₁₄-C₁₇ chlorinated paraffins,all of which are produced by Pioneer (Houston, Tex.).

Fire hazard-reducing agents of the present invention further compriseammonium polyphosphates (APPs), [NH₄PO₃]_(n). The ammoniumpolyphosphates may be straight chained or branched and cross-linkedmolecules. Ammonium polyphosphates are available coated with silanes,melamines or other substances. The present invention is intended toinclude coated or uncoated ammonium polyphosphate formulations.Representative of these APP formulations are FR CROS 484 (uncoated), RFCROS 486 (surface reacted silane coating), and FR CROS 484 (surfacereacted melamine coating), which are all available from Specialchem S.A.(Paris, France).

Fire hazard-reducing agents of the present invention further comprisemixtures of water with polyalkylene glycols (PAGs) or polyol ester(POEs) lubricants optionally with anti corrosion, antiwear, stabilizerand/or lubricity additives. The formulations with water may comprise 30weight percent water or more, such as EMKAROX® HV 45 and EMKAROX® HV 20(PAGs from Uniqema, Gouda, The Netherlands). As the PAG/water andPOE/water as described may also function as a lubricant, additionallubricants may not be necessary. Alternatively, additional lubricantsmay be added to the PAG/water or POE/water mixtures as may be requiredfor lubrication.

Fire hazard-reducing agents of the present invention further compriseperfluorocarbon or perfluoropolyether lubricants. Examples include butare not limited to Krytox® (DuPont, Wilmington, DE),Fomblin® (SolvaySolexis, Italy), and Demnum™ (offered by Daikin America, Inc., Osaka,Japan). Representative lubricants of this type are Krytox® 1531XP orKrytox® GLP series, Fomblin® Z-Dol, Z-Tetraol, AM 2001, or AM 3001,Demnum™ LR-200 or S-65 and other Demnum™ oils. As said perfluorinatedlubricants may also function as a lubricant, no other lubricant may berequired in a composition containing said perfluorinated firehazard-reducing agents. Alternatively, the perfluorinated lubricants maybe included as an additive to the other lubricants as described herein.

Fire hazard-reducing agents of the present invention further comprisemelamines, including melamine (2,4,6-triamino-1,3,5-triazine, CAS no.106-78-1) and homologues and derivatives of melamine. Such melaminehomologues include multi-ring structures such as melam(1,3,5-triazine-2,4,6-triamine-n-(4,6-diamino-1,3,5-triazine-2-yl),melem (2,5,8-triamino-1,3,4,6,7,9,9b-heptaazaphenalene, CAS no.1502-47-2), and melon(poly[8-amino-1,3,4,6,7,9,9b-heptaazaphenalene-2,5-diyl)]). Suchmelamine derivatives include melamine cyanurate and melamine(mono/pyro/poly) phosphates, such as Melapur® MP (melamine monophosphateand Melapur® 200 (a melamine polyphosphate). All these melamines areavailable from Specialchem S.A. (Paris, France).

Fire hazard-reducing agents of the present invention further comprisefluoroketones. The fluoroketones of the present invention consist ofcompounds containing fluorine, carbon, at least one ketone group oxygen,and optionally hydrogen. Such fluoroketones may be represented by theformula R¹COR², wherein R¹ and R² are independently selected fromstraight or branched chain, saturated or unsaturated, aliphatic oralicyclic partially or fully fluorinated hydrocarbon radicals.Additionally, R¹ and R² may be joined to form a cyclic fluoroketonering. The fluoroketones may contain from about 2 to 10 carbon atoms.Preferred fluoroketones contain 4 to 8 carbon atoms. The fluoroketonesof the present invention may further contain heteroatoms, such asoxygen, thus forming additional ketone groups, ether groups, aldehydegroups, or ester groups. Examples of such fluoroketones are1,1,1,2,2,4,5,5,5-nonafluoro-4-(trifluoromethyl)-3-pentanone orperfluoroethyl isopropyl ketone (PEIK, CAS reg. no. 756-13-8);1,1,1,3,4,4,4-heptafluoro-3-(trifluoromethyl)-2-butanone orperfluoromethyl isopropyl ketone (PMIK, Cas reg. no. 756-12-7);1,1,1,2,4,5,5,5-octafluoro-2,4-bis(trifluoromethyl)-3 pentanone;1,1,1,2,4,4,5,5-octafluoro-2-(trifluoromethyl)-3-pentanone;1,1,1,2,4,4,5,5,6,6,6-undecafluoro-2-(trifluoromethyl)-3-hexanone; and1,1,2,2,4,5,5,5-octafluoro-1-(trifluoromethoxy)-4-(trifluoromethyl)-3-pentanone.PEIK is available from 3M™ (St. Paul, Minn.) and the other fluoroketoneslisted may be prepared as described in U.S. Pat. Nos. 3,185,734 and6,478,979 incorporated herein by reference, and J. Am. Chem. Soc., vol84, pp. 4285-88, 1962.

Fire hazard-reducing agents of the present invention further comprisefluoroiodo compounds such as trifluoromethyl iodide (CF₃I, Cas reg. no.2314-97-8).

The concentration of fire hazard-reducing agent in the compositions ofthe present invention will vary depending upon the flammablerefrigerant, fire hazard-reducing agent and lubricant employed. Theconcentration of the fire hazard-reducing agent in any of thecompositions of the present invention may be sufficient to reduceflammability to an acceptable level or eliminate the flammability ofsaid composition entirely. The concentration of fire hazard-reducingagent with respect to flammable refrigerant may be from about 1 weightpercent to about 50 weight percent in the flammable refrigerant. Incompositions of lubricant and fire hazard-reducing agent theconcentration of fire hazard-reducing agent may be from about 1 weightpercent to about 99 weight percent in the lubricant. In compositionscomprising flammable refrigerant, fire hazard-reducing agent andlubricant the concentration of the fire hazard-reducing agent may befrom about 0.5 weight percent to about 50 weight percent with respect tothe complete composition.

The compositions of the present invention that incorporate liquidcomponents may be prepared by any convenient method to combine thedesired amount of the individual components. A preferred method is toweigh the desired component amounts and thereafter combine thecomponents in an appropriate vessel. Agitation may be used, if desired.The fire-hazard reducing agent is charged to a cylinder, to which theliquified (under pressure)refrigerant is added under, under pressure isadded. Optionally, the cylinder is permitted to “roll” to achieve mixingof the fire-hazard reducing agent with the flammable refrigerant. Othermixing techniques include shaking, or by employing a roller, a paintmixer, or any suitable device that will achieve mixing of the componens.

Fire hazard-reducing agents of the present invention may form a solutionor an emulsion in the flammable refrigerant or the lubricant or may bepresent as a solid dispersion in said flammable refrigerant or in saidlubricant. The particles of the solid phase fire hazard-reducing agentmay have median particle size of about 10 micrometers or less.Alternatively, the particles may have median particle size of about 500nanometers or less, or the particles may be nanoparticles with medianparticle size of about 100 nanometers or less. The nanosize solidparticles contained in such a dispersion are preferred.

The solid dispersions of fire hazard-reducing agent in refrigerantand/or lubricant may be prepared by combining the fire hazard-reducingagent with the refrigerant or lubricant and optionally a dispersant.Depending upon the fire hazard-reducing agent, refrigerant and/orlubricant used, it may be appropriate to combine the dispersant with therefrigerant or lubricant first and subsequently add the firehazard-reducing agent to the combination. The combination may be milledto reduce particle size and produce a more uniform dispersion,optionally making use of grinding media.

Milling devices of the present invention include any device or methodthat achieves reduction in the size of particles through a grindingprocess, optionally utilizing grinding media. The milling device can beany that uses an attritor, a tumbling ball mill, a vibratory ball mill,a planetary ball mill, a bead mill, a horizontal media mill, a verticalmedia mill, an annular media mill, a rotor-stator or a high pressure jetmill, such as a Microfluidizer® (Microfluidics™, Newton, Mass.).Preferred milling devices for milling of solid phase fire hazardreducing agents in lubricant are ball mills, bead mills or media mills.For milling solid phase fire hazard reducing agents in flammablerefrigerants, the milling device would require modification for highpressure, due to the pressure of the compressed gas refrigerants.Preferred of the milling devices for the compositions containingflammable refrigerant is a high pressure media mill as disclosed in U.S.patent application Ser. No. 10/476,312, incorporated herein byreference.

In the instance of air or water sensitive solid phase fire hazardreducing agents, milling of the present invention may involve evacuatinggases from the milling device prior to adding of a hydrofluorocarbon tothe milling device, and/or purging the milling device with an inert gasprior to adding of a hydrofluorocarbon to said milling device.

The milling step of the present invention optionally uses grindingmedia, which is added to the milling device prior to milling. Grindingmedia is generally comprised of any material of greater hardness andrigidity than the particle to be ground. The grinding media can becomprised of almost any hard, tough material including, for example,ceramics such as zirconia; nylon and polymeric resins; metals, and arange of naturally occurring substances, such as sand, silica, or chitinobtained from crab shells. Further, grinding media may either consistentirely of a single material that is tough and resilient, or in thealternative, be comprised of more than one material, i.e., comprise acore portion having a coating of tough resilient material adheredthereon. Additionally, the grinding media may be comprised of mixturesof any materials that are suitable for grinding. Any size of grindingmedia suitable to achieve the desired particle size can be utilized.However, in many applications the preferred size range of the grindingmedia will be from about 15 millimeters to about 200 micrometers rangefor continuous media milling with media retention in the mill. Largelyspherical (i.e. close to perfect spheres) media is commonly used,although use of largely cubic (i.e. close to perfect cubes) media isknown. Media aspect ratios (ratio of height to width) are commonly nearabout 1 and seldom exceed about 10. For batch media milling (inattritors) or circulation milling in which slurry and grinding media arecirculated, smaller nonspherical grinding media can be often utilized.

The optional dispersants of the present invention may be cationic,amphoteric, nonionic or anionic. The dispersant used in a composition ofthe present invention will depend on the chemical nature of thedifferent composition components.

The dispersants useful for preparing a dispersion of fire hazardreducing agent in lubricant may be any anionic or non-ionic dispersant,or combinations thereof, found to produce a non-sedimenting dispersioncomposition when combined with synthetic oils and fine particles of thepresent invention. Dispersants that display some of the character ofionic or anionic dispersants, such as amphoteric dispersants, may alsobe used. Either polymeric or non-polymeric dispersants may be used.Combinations of polymeric and non-polymeric dispersants are preferred.

Non-polymeric dispersants are generally molecules with twofunctionalities, one of which acts to anchor the dispersant to aparticle and one which maintains compatibility with the liquid. Theygenerally have molecular weights of less than 1000. Some non-polymericdispersants have multiple identical segments or groups but thesemolecules do not regularly repeat segments (such as in polymers) and aregenerally smaller molecules (less than 1000 MW).

In non-ionic dispersants and anionic dispersants, there is generally ahydrophobic functionality and a hydrophilic functionality. Typicalexamples of hydrophobic segments include alkyl, aryl, alkaryl, siloxane,polysiloxane, fluoroether, and flouroalkyl groups. In anionicdispersants, the hydrophilic group has anionic character. Examples ofthese segments include but are not limited to: carboxylates, sulfonates,sulfates, phosphates, phosphonates, quaternary salts, and amine oxides.Other hydrophilic groups included in non-ionic dispersants include, butare not limited to: ethoxylates or alkoxylates and hydroxylatesincluding saccharides.

Examples of non-ionic dispersants that may be used include the C10-C18N-alkyl polyhydroxy fatty acids and fatty acid amides; C12-C18 alkylethoxylates (“AE”—type surfactants), the C10-C18 glycerol ethers,C10-C18 alkyl alkoxy carboxylates, C10-C18 alkyl polyglycosides, andC6-C12 alkyl phenol alkoxylates. These materials are availablecommercially by various sources. For example, the Triton “X” series,such as X-45, X-100, X-114, and X-102 from Rohm and Haas, are examplesof alkyl phenol alkoxylates of various structures.

Examples of anionic dispersants that may be used include C8-C22 primaryor secondary alkane sulfonates, sulfonated polycarboxylic acids, alkylglyceryl sulfonates, alkyl phenol ethylene sulfates, alkyl phosphates,and sulfosuccinates. Anionic dispersants of the present invention areavailable commercially. Representative sulfosuccinate dispersants areAerosol OT, (Cytec, West Paterson, N.J.), Anionyx 12s (Stepan,Northfield, Ill.), Mackanate DOS-100 (McIntyre, University Park, Ill.),and Monawet MB-100 (Uniqema, New Castle, Del.).

Polymeric dispersants have repeating segments, at least some of whichcontain functionality for anchoring the dispersant to the surface, andgenerally have molecular weights exceeding about 1000. They may behomopolymers, where the segments are all the same, or co-polymers, wherethere are multiple types of segments.

In non-ionic polymeric dispersants, there are generally some segments,which are largely hydrophobic, and others that are largely hydrophilic.In largely non-polar solvents, the hydrophilic portion of the dispersantanchors the dispersant to the particle. In largely polar solvents, thehydrophobic portion of the dispersant anchors the dispersant to theparticle. Typical hydrophilic segments include, but are not limited to,ethoxylates or alkoxylates, highly polar ethers, and hydroxylatesincluding saccharides. Typical hydrophobic segments include, but are notlimited to, alkyl groups, alkylene groups, aryl groups, aromatic groups,fluorocarbons, silicones, hydrophobic ethers (such as styrene oxide,propylene oxide, butylene oxide, and doecyl glycidyl ether) andhydrophobic polyesters such as methycrylate esters, methacrylate esters,and caprolactone. In some non-ionic polymer dispersants, other anchoringstrategies, such as hydrogen bonding, are used and segments are includedin the polymers to create this functionality in the dispersant.

In anionic polymeric dispersants, anionic groups including, but notlimited to carboxylates, sulfonates, sulfates, phosphates, phosphonates,quaternary salts, and amine oxides are incorporated in the polymer, inaddition to other hydrophobic or hydrophilic segments, as describedabove for non-ionic polymeric dispersants.

Non-ionic dispersants of the present invention may be alkoxylatedpolyaromatics, 12-hydroxystearic acid and polyhydroxystearic acid. Arepresentative alkoxylated polyaromatic is Solsperse 27000 (Avecia,Manchester, England).

The dispersants useful for preparing a dispersion of fire hazardreducing agent in flammable refrigerant are generally anionic orcationic compounds that contain a hydrophilic moiety and a hydrophobicmoiety. These dispersant compounds also may have tails containing polargroups such as alcohols. The dispersant hydrophilic moiety comprises acationic (e.g., aliphatic ammonium), amphoteric (e.g., amine betaines),nonionic (e.g., oxyalkylene oligomers, sugar alcohols (e.g., sorbitol),polysorbates, polysaccarides) or anionic (e.g., carboxylate, phosphate,sulfate, sulfonate, sulfosuccinate) group. Additional useful dispersantsinclude fluorosurfactants such as DuPont (Wilmington, DE) Zonyl® brandsurfactants and similar compounds sold by 3M™ (St. Paul, Minn.);derivatives of C₁₂-C₁₅ alcohols; and Propameen group (alkoxylatedamines) from Akzo (Chicago, Ill.). Representative dispersants include:phospholipids (e.g., soy lecithin); polysaccharides (e.g., starch,glycogen, agar, carrageenan); polysorbate 80; Span® 85 (sorbitantrioleate (Uniqema)); Pluronics 25R4; Pluronics P104; Phospholan PS 222,a C12-C15 alcohol phophate (from Akzo); and Sulfopon, a C12-C16 fattyalcohol sulfate(from Cognis, Dusseldorf, Germany); Texapon TB, a TEAlaurel sulfate (Cognis), and Texapon PNSO-L, a sodium C12-C14 ethersulfate (Cognis).

Lubricants of the present invention comprise those suitable for use withrefrigeration or air-conditioning apparatus. Among these lubricants arethose conventionally used in compression refrigeration apparatusutilizing chlorofluorocarbon refrigerants. Such lubricants and theirproperties are discussed in the 1990 ASHRAE Handbook, RefrigerationSystems and Applications, chapter 8, titled “Lubricants in RefrigerationSystems”, pages 8.1 through 8.21, herein incorporated by reference.Lubricants of the present invention may comprise those commonly known as“mineral oils” in the field of compression refrigeration lubrication.Mineral oils comprise paraffins (i.e. straight-chain andbranched-carbon-chain, saturated hydrocarbons), naphthenes (i.e. cyclicparaffins) and aromatics (i.e. unsaturated, cyclic hydrocarbonscontaining one or more rings characterized by alternating double bonds).Lubricants of the present invention further comprise those commonlyknown as “synthetic oils” in the field of compression refrigerationlubrication. Synthetic oils comprise alkylaryls (i.e. linear andbranched alkyl alkylbenzenes), synthetic paraffins and napthenes, andpoly(alphaolefins). Representative conventional lubricants of thepresent invention are the commercially available BVM 100 N (paraffinicmineral oil sold by BVA Oils), Suniso® 3GS and Suniso® 5GS (napthenicmineral oil sold by Crompton Co.), Sontex® 372LT (napthenic mineral oilsold by Pennzoil), Calumet® RO-30 (napthenic mineral oil sold byCalument Lubricants), Zerol® 75, Zerol® 150 and Zerol® 500 (linearalkylbenzenes sold by Shrieve Chemicals) and HAB 22 (branchedalkylbenzene sold by Nippon Oil).

Lubricants of the present invention further comprise those which havebeen designed for use with hydrofluorocarbon refrigerants and aremiscible with refrigerants of the present invention under compressionrefrigeration and air-conditioning apparatus' operating conditions. Suchlubricants and their properties are discussed in “Synthetic Lubricantsand High-Performance Fluids”, R. L. Shubkin, editor, Marcel Dekker,1993. Such lubricants include, but are not limited to, polyol esters(POEs) such as Castrol® 100 (Castrol, United Kingdom), polyalkyleneglycols (PAGs) such as RL-488A from Dow (Dow Chemical, Midland, Mich.),and polyvinyl ethers (PVEs).

Lubricants of the present invention are selected by considering a givencompressor's requirements and the environment to which the lubricantwill be exposed. Lubricants of the present invention preferably have akinematic viscosity of at least about 5 cs (centistokes) at 40° C.

Commonly used refrigeration system additives may optionally be added, asdesired, to compositions of the present invention in order to enhancelubricity and system stability. These additives are generally knownwithin the field of refrigeration compressor lubrication, and includeanti wear agents, extreme pressure lubricants, corrosion and oxidationinhibitors, metal surface deactivators, free radical scavengers, foamingand antifoam control agents, leak detectants and the like. In general,these additives are present only in small amounts relative to theoverall lubricant composition, and are typically used at concentrationsof from less than about 0.1% to as much as about 3% of each additive.

These additives are selected on the basis of the individual systemrequirements. Some typical examples of such additives may include, butare not limited to, lubrication enhancing additives, such as alkyl oraryl esters of phosphoric acid and of thiophosphates. Additionally, themetal dialkyl dithiophosphates (e.g. zinc dialkyl dithiophosphate orZDDP, Lubrizol 1375) and other members of this family of chemicals maybe used in compositions of the present invention. Other antiwearadditives include natural product oils and assymetrical polyhydroxyllubrication additives such as Synergol TMS (International Lubricants).Similarly, stabilizers such as anti oxidants and free radical scavengersmay be employed. Water scavengers may be also be employed if thefire-reducing agent that is being used does not comprise water as acomponent. Compounds in this category can include, but are not limitedto, butylated hydroxy toluene (BHT) and epoxides.

The present invention further comprises a method for reducing firehazard of a flammable refrigerant and/or reducing the fire hazardpresent in a refrigeration or air-conditioning apparatus, said methodcomprising introducing the compositions of the present invention intosaid refrigeration or air-conditioning apparatus. Refrigeration orair-conditioning apparatus include but are not limited to centrifugalchillers, household refrigerator/freezers, residential air-conditioners,automotive air-conditioners, refrigerated transport vehicles, heatpumps, supermarket food coolers and display cases, and cold storagewarehouses. The present invention further comprises a method forreducing fire hazard in or in the vicinity of a refrigeration or airconditioning apparatus, said method comprising:

-   -   (i) combining a fire-reducing agent with a flammable        refrigerant; or    -   (ii) combining fire-reducing agent with a lubricant; and        introducing said combination into a refrigeration or air        conditioning apparatus.

The present invention further comprises a composition, said compositionbeing suitable for replacing non-flammable refrigerant in refrigerationor air conditioning apparatus, comprising:

-   -   (i) flammable refrigerant;    -   (ii) fire hazard-reducing agent; and    -   (iii) optionally a lubricant.

The compositions of the present invention may be suitable asreplacements for refrigerant in stationary or mobile refrigeration orair conditioning apparatus. Such replacements may be suitable for use innew equipment, retrofit for existing equipment that may require somemodifications or as a drop-in replacement in existing equipment (notrequiring any modifications for use). For example, a compositioncomprising the flammable refrigerant R-32 and a fire-hazard reducingagent may serve as a replacement for R-410A (the ASHRAE designation forthe non-flammable refrigerant composition comprised of 50 weight percentR-32 and 50 weight percent R-125). Additionally, a compositioncomprising the flammable refrigerant R-152a and a fire-hazard reducingagent may serve as a replacement for R-134a.

The present invention further comprises a method of using a firehazard-reducing agent in refrigeration or air conditioning apparatus,said method comprising:

-   -   (i) combining said agent with a flammable refrigerant suitable        for use in refrigeration or air conditioning apparatus; or    -   (ii) combining said agent with a lubricant suitable for use in        refrigeration or air conditioning apparatus; or    -   (iii) introducing said agent into refrigeration or air        conditioning apparatus.

The present invention further comprises a method for replacing anon-flammable refrigerant with a flammable refrigerant in arefrigeration or air conditioning apparatus, said method comprisingadding a fire hazard-reducing agent to said flammable refrigerant. Inthe method said non-flammable refrigerant may be R-134a and saidflammable refrigerant may be R-152a. Also, said non-flammablerefrigerant may be R-410A and said flammable refrigerant may be R-32.The method comprises use of fire hazard-reducing agents as describedherein.

EXAMPLES

The following examples are meant to demonstrate the reduced probabilityof fire occurring should a refrigerant composition containing aflammable refrigerant and a fire hazard reducing agent leak from arefrigeration or air conditioning apparatus. An apparatus wasconstructed to perform measurements and to allow observations of flamecharacteristics based upon ASTM Test Method D 3065-94, a Standard Testfor Flammability of Aerosols. The ASTM test was modified by using a gastorch as an ignition source, in order to increase the stability andreproducibility of the test.

In this test, the material to be tested was charged to a pressurizedvessel that had been fitted with a metered discharge valve and aprecision spray nozzle having a diameter of 0.016 inches. The valve andnozzle assembly allowed a discharge rate of about 1.1 to 1.2 grams persecond of the mixture charged to the vessel, as a finely dispersedaerosol mist.

In each test, the composition to be tested was discharged through thenozzle and across the same gas burner flame. The length of the burningplume of the escaping gas mixture was measured, as well as the flamequality, as determined by color, intensity, and cross sectional shape orsize of the flame.

In the following examples, PEIK is perfluoroethylisopropyl ketone(1,1,1,2,2,4,5,5,5-nonafluoro-4-(trifluoromethyl)-3-pentanone, CAS reg.no. 756-13-8) from 3M™ (St. Paul, Minn.). Syn-O-Ad 8784 is a butylatedtriphenyl phosphate from Akzo Nobel (Arnhem, the Netherlands). Durad 620is a tert-butylated triphenyl phosphate from Great Lakes ChemicalCorporation (GLCC, West Lafayette, Ind.). Durad 220 and 110 areiso-propylated triphenyl phosphates also from GLCC. Trifluoromethyliodide is CF₃I, and is available from Aldrich Chemical (Milwaukee,Wis.).

Example 1

Baseline flame characteristics were established by discharging pureflammable refrigerant, HFC-152a (DuPont, Wilmington, Del.) into theignitor flame and recording the flame characteristics. Following theestablishment of the baseline, a combination of refrigerant and firehazard-reducing agent was discharged as an aerosol into the ignitorflame. The resulting flame, if present, was observed and the flamecharacteristics recorded. The results are shown in Table 1 below.

TABLE 1 Fire Hazard- Reducing Refrigerant, Agent, Flame concentrationconcentration Length Flame (wt %) (wt %) (inches) Quality ObservationsHFC-152a, 100 none 12 mild, light- baseline - blue flame HFC onlyHFC-152a, 91 PEIK, 9 2 very faint, substantial blue flame reduction offlame HFC-152a, 90 PEIK, 10 1 very faint, substantial blue flamereduction of flame HFC-152a, 80 PEIK, 20 no no flame elimination flameof flame HFC-152a, 91 Syn-O-Ad 8784, 3 weak, substantial yellowreduction of flame flame HFC-152a, 50 Durad 620, 50 4 weak, substantialyellow reduction of flame flame HFC-152a, 91 Durad 620, 9 6 yellowsubstantial flame reduction of flame HFC-152a, 91 Durad 220, 9 6.5bushy, substantial yellow reduction of flame flame HFC-152a, 91 Durad110, 9 6.5 bushy, substantial yellow reduction of flame flameThe results show the flame length and intensity are reduced, and in onecase the flame eliminated, by addition of fire hazard reducing agent torefrigerant HFC-152a.

Example 2

Baseline flame characteristics were established by discharging a mixtureof refrigerant and lubricant, HFC-152a and UCON® RL-488 PAG lubricant(Dow Chemical Corporation, Midland, Mich.), into the ignitor flame andrecording the flame characteristics. Following the establishment of thebaseline, a combination of HFC-152a, PAG and fire hazard-reducing agentwas discharged as an aerosol into the ignitor flame. The resultingflame, if present, was observed and the flame characteristics recorded.The results are shown in Table 2 below.

Antimony pentoxide was introduced to the test mixture as a dispersion inPAG lubricant. The antimony pentoxide (Sb₂O₅) dispersion was prepared ina laboratory media mill consisting of a baffled beaker filled withspherical ceramic media (0.4-0.6 mm diameter). The agitator blade wasrotated at a tip speed of 10 meters/second by the use of a motor andshaft to create shear within the media. Thirty grams of antimonypentoxide powder, A1588LP from Nyacol® Corporation (Ashland, Mass.), wasadded to 120 grams of RL-488 PAG lubricant in the baffled media mill andthe slurry was agitated for about 2 hours. The resulting dispersion was20 weight percent (wt %) Sb₂O₅ in PAG.

Iron carbonate was also introduced to the test mixture as a dispersionin PAG lubricant. The iron carbonate (FeCO₃) dispersion was preparedusing the same procedure described above for the antimony pentoxidedispersion. The resulting dispersion was 16 weight percent FeCO₃ in PAG.

TABLE 2 Fire hazard- Refrigerant, reducing agent, Flame conc. lubricant,concentration Length Flame conc. (wt %) (wt %) (inches) QualityObservations HFC-152a, 90 None 18 blue, bushy, baseline PAG RL-488, 4 to6 inches with PAG 10 diameter lubricant HFC-152a, 90 Sb₂O₅ 16 yellow, 3inch significant PAG RL-488, A1588P, 2.0 diameter reduction of 8.0 weakflame flame HFC-152a, 90 FeCO₃, 1.6 4 yellow flame substantial PAGRL-488, reduction of 8.4 flame HFC-152a, 80 Syn-O-Ad 2 weak yellowsubstantial PAG RL-488, 8784, 10 flame reduction of 10 flame HFC-152a,70 Syn-O-Ad 2 very substantial PAG RL-488, 8784, indistinct reduction of10 10 CF₃I, 10 weak flame flame HFC-152a, 70 CF₃I, 20 no no flameelimination PAG RL-488, flame of flame 10 HFC-152a, 90 PEIK, 5 3 faintblue, substantial PAG RL488, 5 yellow reduction of tipped flame flameHFC-152a, 80 PEIK, 10 no no flame elimination PAG RL-488, flame of flame10 HFC-152a, 70 PEIK, 10 1 very weak substantial PAG RL-488, flamereduction of 20 flame

The results show the flame length and intensity are reduced, and in twocases the flame is eliminated, by addition of fire hazard reducing agentto HFC-152a and PAG RL-488.

1. A composition comprising: (i) at least one flammable refrigerant; and(ii) at least one fire hazard-reducing agent comprising an antimonyoxide.
 2. The composition of claim 1 wherein said flammable refrigerantis selected from the group consisting of hydrofluorocarbons,fluoroethers, hydrocarbon ethers, hydrocarbons, ammonia and mixturesthereof.
 3. The composition of claim 1 wherein said flammablerefrigerant is selected from hydrofluorocarbons, hydrocarbons,hydrocarbon ethers, and mixtures thereof.
 4. The composition of claim 3wherein said flammable refrigerant is selected from the group consistingof difluoromethane, fluoromethane, 1,1,1- trifluoroethane,1,1-difluoroethane, fluoroethane, 1,1,1-trifluoropropane, propane,propylene, cyclopropane, n-butane, isobutane, n-pentane, dimethyl ether,and mixtures thereof.
 5. The composition of claim 1, wherein saidflammable refrigerant is a mixture, said mixture comprising at least onenon-flammable refrigerant.
 6. the composition of claim 5, wherein saidnon-flammable refrigerant is selected from the group consisting ofR134a, R23, R125, R236fa, R245fa, carbon dioxide, and mixtures thereof.7. The composition of claim 1 further comprising at least one lubricantsuitable for use with refrigeration or air-conditioning apparatus. 8.The composition of claim 1 further comprising at least one additiveselected from the group consisting of anticorrosion, anti-wear,stabilizer and lubricity additives.
 9. The composition of claim 1wherein the flammable refrigerant comprises R-32.
 10. The composition ofclaim 1 wherein the flammable refrigerant comprises R-152a.
 11. A methodfor reducing fire hazard in refrigeration apparatus or air conditioningapparatus, said method comprising introducing the composition of claim 1into said refrigeration apparatus or air conditioning apparatus.
 12. Acomposition comprising: (i) a fire hazard-reducing agent suitable foruse with a flammable refrigerant comprising at least one antimony oxide;(ii) a flammable refrigerant; and (iii) a lubricant suitable for usewith refrigeration or air conditioning apparatus.
 13. The composition ofclaim 1 or 12 wherein said fire hazard reducing agent is an oxide salt.14. The composition of claim 1 or 12 wherein said fire hazard reducingagent is selected from the group consisting of antimony trioxide andantimony pentoxide.
 15. The composition of claim 7 or 12 wherein saidlubricant is selected from the group consisting of mineral oils,paraffins, naphthenes, synthetic paraffins, alkylbenzenes,poly-alpha-olefins, polyalkylene glycols, polyvinyl ethers, polyolesters and mixtures thereof.
 16. A method of using a fire-hazardreducing agent comprising an antimony oxide, said method comprisingcombining a flammable refrigerant with said fire-hazard reducing agentin a refrigeration or air conditioning apparatus.